Field
The present invention relates to a surface-mount type light emitting device and an image display unit using the same.
Description of the Related Art
Lamp type LEDs are often used as light emitting devices that configure respective pixels of an image display device (a display) placed in an outdoor location. However, from the standpoint of downsizing, thinning, or heat dissipation, surface-mount type (SMD type) LEDs are gradually becoming popular.
Following technologies are proposed as such a surface-mount type light emitting device. For example, JP H10-261821 A (see FIG. 9B) discloses a light emitting device that includes a resin stem and a protrusive part which covers the whole upper surface of the resin stem and the whole upper side surface with a light transmissive thermosetting resin, thereby improving the moisture resistance and the light emitting efficiency. Also, JP 2006-049442 A (see FIG. 1) discloses a light emitting device that has a heat dissipation member provided on the rear surface of a lead frame via a conductive layer including a metal, thereby improving the heat dissipation characteristic. Also, JP 2006-093738 A (see FIGS. 4 and 10) discloses a light emitting device that has a first recess which is formed in the stem and where a semiconductor element is mounted and a second recess formed around the first recess in order to make the amount of encapsulation material encapsulating the semiconductor element always constant.
When the light emitting devices disclosed in JP H10-261821 A, JP 2006-049442 A, and JP 2006-093738 A are used as pixels of an image display device placed in an outdoor location, for example, as shown in FIG. 11A, in order to prevent moisture due to rain water, humidity, etc., from entering into the interior of a light emitting device 101, a side (a surrounding area) of the light emitting device 101, in particular, a boundary between a package 110 and a lead frame 120 where moisture is likely to enter is covered by a waterproof resin 102 formed of a silicon resin or the like.
However, the surface-mount type light emitting devices are small in height in comparison with the lamp type light emitting devices, so that the amount of waterproof resin that can be used is little by what corresponds to such smallness. Hence, according to the conventional light emitting device 101, as shown in FIG. 11B, when it is used for a long period, the waterproof resin 102 repeats expansion and shrinkage due to heat by sunlight or the like, and the waterproof resin and the package resin are deteriorated by moisture and ultraviolet, and thus the waterproof resin 102 may be peeled from the package 110.
As shown in FIG. 11B, when such peeling of the waterproof resin 102 reaches the lead frame 120, moisture enters to a light emitting element 130 inside the light emitting device 101 from the boundary between the package 110 and the lead frame 120, and the light emitting element 130 becomes unable to emit light.
The present invention has been made in view of such a problem, and it is an object of the present invention to provide a surface-mount type light emitting device and an image display unit which suppress peeling of a waterproof resin to a boundary between a package and a lead frame where moisture is likely to enter in order to prevent the moisture like rain water from entering therein even if the waterproof resin covering a side of the light emitting device starts peeling and which are excellent in waterproofing.